A primary characteristic of scoliosis is that an elongate central axis of the spine is curved rather than straight, when viewed posteriorly or anteriorly. Such cases of scoliosis can vary between minor and severe. In more severe cases, one treatment is to intervene surgically, aligning the individual vertebra of the spine together to reform the elongate central axis of the spine to be linear (when viewed posteriorly or anteriorly), and then to fuse certain of the disk spaces between adjacent vertebrae to hold the vertebrae in this new position.
To assist in holding the vertebrae in the desired position during fusion of adjacent vertebrae together, it is known to place pedicle screws into the pedicles of the vertebrae and to attach heads of the pedicle screws to one or more elongate spine rods. Such fusion with pedicle screws and spine rods is also known to treat other conditions other than scoliosis, such as where injury has occurred to the spine or disks within the spine have degenerated and fusion is indicated. The pedicle screws and spine rods generally remain implanted even after the adjacent vertebra have fused together and are formed of biocompatible materials to minimize any adverse consequences associated with such permanent implantation.
One such system that provides the hardware components for such procedures is the “Universal Spine System” (“USS”) provided by Synthes, Inc. whose United States headquarters is in West Chester, Pa. The USS includes pedicle screws and spine rods as well as extension posts for pedicle screws and other associated hardware.
Certain cases of scoliosis, as well as potentially other conditions, are characterized in that at least one vertebra is rotated about the central axis of the spine out of alignment relative to a desired orientation for the vertebra. Such a vertebra can be either in a proper position but only in an undesirable rotation or can be both in an improper position and rotated to an improper orientation. Prior art spinal fusion hardware and procedures, including those in Synthes' USS, have not adequately dealt with such vertebral mis-rotation. Thus leaving the patient to suffer from the consequences of such mis-rotation.
Furthermore, when a vertebra is mis-rotated into an improper position, a surgeon is to some extent thwarted in properly placing pedicle screws and properly attaching heads of the pedicle screws to an adjacent elongate spine rod. For instance, where a vertebra is mis-rotated and a pedicle screw is attached to the pedicle of the vertebra in the typical fashion, the head of the pedicle screw is not where it needs to be to attach to the elongate and substantially linear spine rod.
Ligaments and other bodily structures tend to hold a mis-rotated vertebra in its mis-rotated position, making it difficult for the surgeon to manually de-rotate the vertebra to is proper position and hold it in this de-rotated position while anchoring it to the spine rod. Accordingly, a need exists for a method and apparatus for de-rotating a mis-rotated vertebra and to hold the mis-rotated vertebra in the proper de-rotated position, so that an elongate spine rod can be affixed to the pedicle screws, thus holding the mis-rotated vertebra can be held in its proper and de-rotated position while adjacent vertebra fuse together.
While this problem of mis-rotation of vertebra is described in the context of scoliosis and other spine conditions where fusion of adjacent vertebra together is indicated, de-rotation of mis-rotated vertebra could conceivably also beneficially be provided complimentary to procedures on the spine other than spinal fusion, such as disk replacement procedures or disk therapy procedures or other spinal procedures that do not involve vertebral fusion.